In known vehicle seats, the strut is the bottom rod of a resilient telescopic arm whose two ends are pivotally mounted respectively on the rear face of the back and on the bottom face of the retractable table.
The arm is compressed when the table is retracted and it is extended when the table is in its deployed position, and in that position it holds the table substantially perpendicular to the rear face of the back.
Unfortunately, such an arm is relatively expensive.
In addition, when the table is in its deployed position, the arm possesses a degree of operating slack that rattles while the vehicle is moving.